Stratigraphic intervals characterized by varied and complex styles of soft-sediment deformation structures are well preserved in Miocene and Late Pleistocene to Holocene deposits of a sedimentary ...basin located in Northeastern Brazil. The Miocene strata, represented by the Barreiras Formation, record only brittle structures, including numerous faults and fractures with straight and high angle-dipping planes that are often filled with sands derived from overlying beds. Folds consisting of broad anticlines and synclines are also present in this unit. The Late Pleistocene to Holocene deposits, named Post-Barreiras Sediments, contain an indurated sandy package with a large variety of ductile and brittle deformation structures (i.e., massive sandstones with isolated sand fragments and breccias, undulatory strata, sand dykes and diapirs, sinks and bowls, pebbly pockets, plunged sediment mixtures, fitted sand masses, cone-shaped cracks, fault grading and sedimentary enclaves). These features, confined to sharp-based stratigraphic horizons that progressively grade downward into undisturbed deposits, are related to seismic shocks of high surface-wave magnitude (i.e., Ms
>
5 or 6). Amalgamated seismites suggest that previously formed seismites were affected by subsequent seismic-wave propagation. Seismic waves caused by activity along one, or most likely, several tectonic structures would have propagated throughout the depositional environment, producing laterally extensive seismites. The close proximity to earthquake epicenters would have promoted pervasive re-sedimentation due to pore overpressure, resulting high volumes of massive sandstones and breccia. The similarity between deposits with correlatable strata from many other areas along the Brazilian coast allows raise the hypothesis that the seismic episodes might have affected sedimentation patterns in a large (i.e., extension of several hundreds of kilometers) geographic area. Thus, the modern seismicity recorded along Northeastern Brazil was recurrent during the Quaternary and, perhaps, also in the Pliocene. The estimated high magnitude of the seismic events and the great regional extent of the affected area demonstrate that the Brazilian coast experienced tectonic stress through the last geological episodes of its evolution, which would have favored sediment accumulation and penecontemporaneous re-sedimentation. This geological context is unexpected in a passive margin, inducing to revisit the debate on how active is a passive margin.
Lensless, coherent X-ray diffraction microscopy has been drawing considerable attentions for tomographic imaging of whole human cells. In this study, we performed cryogenic coherent X-ray diffraction ...imaging of human erythrocytes with and without malaria infection. To shed light on structural features near the surface, "ghost cells" were prepared by the removal of cytoplasm. From two-dimensional images, we found that the surface of erythrocytes after 32 h of infection became much rougher compared to that of healthy, uninfected erythrocytes. The Gaussian roughness of an infected erythrocyte surface (69 nm) is about two times larger than that of an uninfected one (31 nm), reflecting the formation of protein knobs on infected erythrocyte surfaces. Three-dimensional tomography further enables to obtain images of the whole cells with no remarkable radiation damage, whose accuracy was estimated using phase retrieval transfer functions to be as good as 64 nm for uninfected and 80 nm for infected erythrocytes, respectively. Future improvements in phase retrieval algorithm, increase in degree of coherence, and higher flux in combination with complementary X-ray fluorescence are necessary to gain both structural and chemical details of mesoscopic architectures, such as cytoskeletons, membraneous structures, and protein complexes, in frozen hydrated human cells, especially under diseased states.
Abstract Removing dietary phytoestrogens causes obesity and diabetes in adult male rats. Based on the facts that hypothalamic food intake control is disrupted in phytoestrogen-deprived animals and ...that several steroids affect food intake, we hypothesized that phytoestrogen withdrawal alters the expression of hypothalamic steroidogenic enzymes. Male Wistar rats fed with a high-phytoestrogen diet from conception to adulthood were subjected to phytoestrogen withdrawal by feeding them a low-phytoestrogen diet, or a high phytoestrogen–high fat diet. Withdrawal of dietary phytoestrogens increased 3β − HSD and ARO gene expression and decreased those of 5αR-1. This is a direct effect of the lack of dietary phytoestrogens and not a consequence of obesity, as it was not observed in high-fat fed rats. Phytoestrogen withdrawal and high-fat diet intake reduced hypothalamic expression of ERα correlated with low levels of ERα-O, ERα-OS and ERα-OT transcripts. Variations in gene expression of steroidogenic enzymes may affect the content of neurosteroids. As neurosteroids are related to food intake control, the changes observed may be a novel mechanism in the regulation of energy balance in obese phytoestrogen-deprived animals. In rats, steroidogenesis and estrogen receptor signaling appear to be altered by phytoestrogen withdrawal in the rat. The ubiquity of phytoestrogens in the diet and changing intakes or withdrawal suggest that aspects of human health could be affected based on the rat and warrant further research.
This work integrates geomorphological, sedimentological, and palynological data with radiocarbon dating, as well as δ13C, δ15N, and C/N from sedimentary organic matter to provide a model of mangrove ...dynamics during the evolution of a wave-dominated delta in Southeastern Brazil. Mangrove dynamics are analyzed within the context of millennial and secular climatic and sea-level changes. Tidal flats, positioned at highest limit of the intertidal zone along the edge of a lagoon sheltered by beach ridges, were occupied by wetlands represented by mangrove and herbaceous vegetation during the mid-Holocene high sea level. After considering the relative sea-level fall and relatively higher fluvial sediment discharge, during the last ~6350 years, progradation took place along this shoreline, resulting in extensive beach ridge deposits that overlie transgressive muds. This process led to loss of mangrove area. Similar dynamics were repeated at ~3043 cal. yr BP, although in a relatively more distal (i.e. seaward) position. Between ~1337 and ~900 cal. yr BP, a tidal flat attached to the edge of a lagoon near the modern coastline was colonized by herbaceous vegetation (C4 plants). The next phase, which occurred between ~900 and ~400 or ~100 cal. yr BP, is marked by the transition from herbaceous to mangrove tidal flats with an increased trend of terrestrial organic matter. During the recent centuries, a mangrove vegetation became established, and there was an increased trend of estuarine-derived organic matter. This mangrove phase, recorded during the last century(ies), may be due to a relative sea-level rise. Under this scenario, erosion of beach ridges and expansion of lagoons and mangroves are expected along the littoral of the State of Espírito Santo in Southeastern Brazil.
Alpine orogens in the central Mediterranean region have revealed the concomitance of crustal extension in back-arc domain and crustal shortening in frontal domain. Quantitative data of deformation in ...the frontal orogenic wedges are necessary to understand how the shortening-extension pair evolves in terms of structures, orogenic transport, timing, and exhumation rate. This paper deals with kinematics and ages of the frontal thrust systems of the Calabria-Peloritani Arc (Italy) exposed in the eastern Sila Massif. We first present structural fieldwork, onshore and offshore well log data, and new apatite fission-track (AFT) thermochronology. Then, we describe the structural architecture of the studied area as an ENE-verging stacking of thrust sheets involving basement units and syn-orogenic sediments. The AFT study documents that thrust sheets entered the partial annealing zone from 18Ma to 13Ma. This Early-Middle Miocene thrusting phase was coeval with exhumation of high-pressure/low temperature metamorphic rocks in the hinterland of the orogen (Coastal Chain area), mainly driven by top-to-the-W extensional tectonics. Opposite kinematic shear senses (contractional top-to-the-E and extensional top-to-the-W) and different exhumation rates (slow in the frontal, more rapid in the hinterland) are framed in a tectonic scenario of a critically tapered orogenic wedge during the eastward retreating of the Apennine slab.
► Structural geology of the frontal thrust in the eastern Sila Massif (Calabrian-Peloritan Arc). ► New thermochronology data performed on granitoid sheets involved in thrusting. ► Miocene tectonic evolution for the Calabrian-Peloritani orogenic wedge.
What controls the formation of patchy substrates of white sand vegetation in the Amazonian lowlands is still unclear. This research integrated the geological history and plant inventories of a white ...sand vegetation patch confined to one large fan-shaped sandy substrate of northern Amazonia, which is related to a megafan environment. We examined floristic patterns to determine whether abundant species are more often generalists than the rarer one, by comparing the megafan environments and older basement rocks. We also investigated the pattern of species accumulation as a function of increasing sampling effort. All plant groups recorded a high proportion of generalist species on the megafan sediments compared to older basement rocks. The vegetation structure is controlled by topographic gradients resulting from the smooth slope of the megafan morphology and microreliefs imposed by various megafan subenvironments. Late Pleistocene-Holocene environmental disturbances caused by megafan sedimentary processes controlled the distribution of white sand vegetation over a large area of the Amazonian lowlands, and may have also been an important factor in species diversification during this period. The integration of geological and biological data may shed new light on the existence of many patches of white sand vegetation from the plains of northern Amazonia.
The role of regional extension on the rise and emplacement of granites in the crust is still debated. Pluton ascent and emplacement widely occurred in Tuscany (Italy) since late Miocene during the ...post-orogenic collapse of the inner Apennines, and are presently occurring in the geothermal areas of Amiata and Larderello. Tuscany offers a preferred test site to study the role of regional extension on pluton ascent and emplacement at different crustal levels. Ductile extension enhanced the segregation and ascent of granitic melts in the lower crust, controlling pluton emplacement in correspondence with the brittle–ductile transition. In the brittle crust, magma ascent occurred through subvertical faults and fractures compatible with the regional extension direction; pluton emplacement mainly occurred by means of roof lifting. The case of Tuscany suggests that the extensional structures enhance melt segregation and ascent in the ductile crust, but are not efficient alone to provide a pathway for the ascent of granitic magmas in the brittle-extending crust. The estimated magmatic strain rates due to pluton emplacement in the geothermal areas are much larger than the regional tectonic strain rates. This suggests that regional tectonics did not control magma emplacement in the brittle crust and explains why nontectonic processes (roof lifting) accommodated the space required for pluton emplacement.
The characterization and mapping of paleoweathering surfaces, as well as their associated deposits, throughout the northeastern Amazonia can be a useful tool for inter-basin stratigraphic ...correlations and for establishing the evolution of landscapes and climates through time. This type of investigation has led to the recognition of five weathering surfaces developed from the Upper Cretaceous through the Quaternary, designated here as S1 to S5. Surface S1 occurs at the top of Late Cretaceous deposits, represented by the Ipixuna/Cujupe succession, as well as on older Precambrian and Paleozoic rocks. Surface S2 marks the top of an indurated, massive, semi-flint
1
1
The term semi-flint is applied here for a flint-like fire clay consisting of indurated kaolinite, which develops no plasticity when grounds up.
unit. For cases in which surfaces S1 and S2 are amalgamated, a thick, lateritic paleosol displaying hexagonal, branched concretions is present. Surface S3 occurs at the top of the Pirabas and lower portion of the Barreiras Formations of Late Oligocene/Early Miocene age, and it is also associated with paleosol, but has no lateritization. When surface S3 is amalgamated with surfaces S1 and S2, bauxite is present in association with the underlying laterites. Surface S4 bounds the top of the middle to upper Barreiras Formation of Middle Miocene age, as well as correlatable deposits known as the Belterra Clay. This surface is marked by a lateritic paleosol having columnar concretions. Surface S5 occurs between a lower unit consisting of massive, light red sands of the Plio-Pleistocene Post-Barreiras 1 sediments and an upper unit of yellow, eolian sands of the Holocene Post-Barreiras 2 Sediments.
The paleoweathering surfaces present in the northeastern Amazonia enable the reconstruction of several depositional episodes represented by thin (only few meters thick) sedimentary units from the Late Cretaceous to the Quaternary. The creation of new accommodation space on subsiding areas gave rise to sediment accumulation during transgressions. Intervening weathering surfaces formed during significant falls in relative sea-level, associated with tectonically stable episodes. The overprinting of weathering surfaces formed during different times, and thus under different climatic conditions, seems to have been crucial for the development of the various weathering products observed throughout the region, which include economically important laterites, bauxites, semi-flint beds and kaolin deposits. This paper shows that the genesis of these deposits was controlled by the complex interplay of tectonics, climate, sediment deposition and erosion, resulting in a complex evolution of paleolandscapes.
Late Quaternary deposits in the northeastern Brazil have been scarcely investigated, despite their relevance to the discussion of the post-rift evolution of the South American passive margin within ...the context of landform, sea level and tectonic deformation. Sedimentological, stratigraphic and morphological characterization of these deposits, referred as Post-Barreiras Sediments, led to their distinction from underlying Early/Middle Miocene strata. Based on optically stimulated luminescence (OSL) dating, two sedimentary units (PB1 and PB2) were recognized and related to the time intervals between 74.8±9.3 and 30.8±6.9ka, and 8.8±0.9 and 1.8±0.2ka, respectively. Unit PB1 consists of indurated sandstones and breccias either with massive bedding or complex types of soft sediment deformation structures generated by contemporaneous seismic activity. Unit PB2 is composed of massive sands or sands related to structures developed by dissipation of dunes. The present work, focusing on the Post-Barreiras Sediments, discusses landform, sea level and tectonics of the eastern South American passive margin during the latest Quaternary. Non-deposition and sub-aerial exposure related to the Tortonian worldwide low sea level combined with tectonic quiescence followed the Miocene transgression. Tectonic deformation in the latest Pleistocene created space to accommodate unit PB1 in downthrown faulted blocks and, perhaps, also synclines produced by strike–slip deformation. Although deposition of this unit was simultaneous with the progressive fall in sea level that followed the Last Interglacial Maximum, punctuated rises combined with land subsidence led to marine deposition close to the modern coastline. Renewed subsidence in the Holocene gave rise to accommodation of the Post-Barreiras Sediments. Most of unit PB2 was deposited during the Holocene Transgression, but it is not composed of marine sediments, which suggests either an insignificant rise in relative sea level or aeolian reworking of thin transgressive sands. The data presented here lead to a review of the evolution of the South American passive margin based on assumptions of uniform sedimentation and undeformed planation surfaces over a wide coastal area of the northeastern Brazil.
►Facies, stratigraphy, morphology and LOE age of Quaternary deposits in Brazil. ►Unit PB1=74.8±9.3 to 30.8±6.9ka and Unit PB2=8.8±0.9 to 1.8±0.2ka. ►Deposition due to tectonic reactivation rather than sea level change. ►South American passive margin tectonically active during the latest Quaternary.
Supported lipid bilayers (SLBs) are ideal platforms for the study of membrane proteins and function. Assembly of functional SLBs in an array format would lead to a breakthrough in high-throughput ...screening of membrane-associated processes, e.g., drugs binding to transmembrane proteins. We report the formation of SLBs from the rupture of anionic vesicles in the presence of Ca(2+) ions on ITO-coated surfaces and characterise the assembly and SLB properties. Furthermore, the formation, manipulation and regeneration of SLBs adsorbed on ITO microelectrode array spots using an electric potential switch are demonstrated. This platform enables addressable assembly and the study of electrochemically mediated membrane processes in a microarray format which can be regenerated in situ.
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